1. Field of the Invention
The present invention relates to an in-vehicle fuel cell system, including a fuel cell stack formed by stacking a plurality of power generation cells, and which is mounted in a vehicle.
2. Description of the Related Art
A polymer electrolyte fuel cell employs a membrane electrode assembly (electrolyte electrode assembly), which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. The electrolyte membrane forms a polymer ion exchange membrane. The membrane electrode assembly, together with separators sandwiching the membrane electrode assembly, make up a unit of a power generation cell (unit cell) for generating electricity. In use, generally, a predetermined number of unit cells are stacked together to form a fuel cell stack.
In general, a fuel cell stack of this type is mounted in a vehicle such as an automobile to make up a fuel cell vehicle (vehicle equipped with a fuel cell). In order to mount the fuel cell stack in the fuel cell vehicle, together with a coolant supply mechanism and a reactant gas supply mechanism connected to the fuel cell stack, various techniques have been adopted.
For example, Japanese Laid-Open Patent Publication No. 2003-63257 discloses a structure for mounting a fuel cell stack in a vehicle. As shown in FIG. 10, a fuel cell stack 1 is mounted in a vehicle 2. Coolant pipes 4, for supplying/discharging a coolant to/from the fuel cell stack 1, and gas pipes for supplying/discharging reactant gases to/from the fuel cell stack 1, are connected to an end plate 3 of the fuel cell stack 1, which is provided on the front side of the vehicle 2.
The gas pipes include fuel gas pipes 5 for supplying/discharging a fuel gas to/from the fuel cell stack 1, and oxygen-containing gas pipes 6 for supplying/discharging an oxygen-containing gas to/from the fuel cell stack 1.
The coolant pipes 4, the fuel gas pipes 5, and the oxygen-containing gas pipes 6 are provided on the front side of the vehicle 2 relative to the fuel cell stack 1, and the coolant pipes 4, the fuel gas pipes 5, and the oxygen-containing gas pipes 6 are connected to a compressor 7. A radiator fan 8 is provided on the front side of the vehicle 2. The radiator fan 8 supplies a cooling wind to heated regions of the coolant pipes 4, the fuel gas pipes 5, and the oxygen-containing gas pipes 6, which are heated by the compressor 7.
In Japanese Laid-Open Patent Publication 2003-63257, the coolant pipes 4, the fuel gas pipes 5, and the oxygen-containing gas pipes 6 are connected to the end plate 3, wherein all of the coolant pipes 4, the fuel gas pipes 5, and the oxygen-containing gas pipes 6 are provided on the front side of the vehicle 2. Thus, the piping structure is complicated and the space required for providing such pipes is large.
Further, in addition to various auxiliary devices, for example, a humidifier for humidifying the reactant gases is provided on the front side of the vehicle 2. Thus, the piping structure becomes even more complicated, and the length of the pipes is large. As a result, pressure losses occur, and further, the weight of the pipes is disadvantageously heavy.
Further, Japanese Laid-Open Patent Publication No. 2001-30771 discloses a fuel cell supporting apparatus 1a for a vehicle. As shown in FIG. 11, the supporting apparatus 1a includes a fuel cell 2a, with support members 3a that support the fuel cell 2a. The fuel cell 2a is formed by alternately stacking unit cells 4a and separators 5a. Plates 6a and 7a are provided at opposite ends of the fuel cell 2a in the stacking direction, wherein the stacking direction of the fuel cell 2a matches the longitudinal direction of the vehicle.
The support members 3a include a first support member 8a, for supporting the plate 6a on a front side thereof, and a second support member 9a, for supporting the plate 7a on the rear side thereof.
The first support member 8a supports the fuel cell 2a with respect to a force that acts to move the fuel cell 2a forward relative to the vehicle, e.g., in the event of sudden braking during traveling, or in the event of a head-on collision. The first support member 8a supports the fuel cell 2a such that the fuel cell 2a cannot move toward the front side of the vehicle.
The second support member 9a supports the fuel cell 2a, such that the fuel cell 2a is movable toward the rear side of the vehicle, in the event of sudden start or sudden acceleration of the vehicle, wherein the fuel cell 2a is movable in any of forward, backward, upward, and downward directions.
In the fuel cell 2a, in addition to various auxiliary devices, for example, a humidifier for humidifying reactant gases is used. Thus, dedicated support members for supporting devices such as the humidifier are required, in addition to the support members for supporting the fuel cell 2a. Consequently, in the conventional technique, since dedicated support members are required for respective devices, the number of components is considerably large, the space required for providing such devices is large, and the overall weight of the equipment is heavy.
Further, in a fuel cell system disclosed in U.S. Pat. No. 6,596,425, as shown in FIG. 12, an air filter 2b and a compressor 3b are provided in a channel 1b that supplies air (oxygen-containing gas) to a fuel cell (not shown).
A water remover 5b is provided in an off gas channel 4b, which serves as a passage for off gases discharged from the cathode of the fuel cell (not shown). The water remover 5b removes water contained in the off gas that is discharged from the cathode, and supplies the water to a medium channel 6b. The water supplied to the medium channel 6b is mixed with air flowing through the channel 1b in order to humidify the air.
According to the disclosure, the medium channel 6b includes a heat channel section 7b. Electricity is supplied to the heat channel section 7b from a vehicle battery, or from the fuel cell, in order to heat the heat channel section 7b. Thus, the water supplied from the medium channel 6b into the channel 1b is maintained in a liquid state, and freezing of the water is prevented.
In U.S. Pat. No. 6,596,425, the heat channel section 7b is provided in the medium channel 6b, and electricity needs to be supplied to the heat channel section 7b from the battery or from the fuel cell. Thus, uneconomically, excessive electricity is consumed. Further, the number of components is large, the structure is complicated, and the cost for such equipment is large.